The present invention relates to certain new macrolide antibiotics which are derivatives of Mycoplanecin.
Mycoplanecin is the subject of co-pending U.S. application Ser. No. 41,501, filed May 22, 1979 issued as U.S. Pat. No. 4,336,249 and has the formula (I) given above except that, in Mycoplanecin, R represents the group: ##STR2##
As disclosed in the aforementioned co-pending application, Mycoplanecin has valuable antibiotic properties against a variety of microorganisms, but most especially against microoganisms of the genus Mycobacterium. Mycoplanecin also has a rather low toxicity and, as a result, is expected to be of considerable value in chemotherapy. However, we have now found that the biological availability of Mycoplanecin on administration to animals by the usual routes is rather low and this may restrict, to some extent, the therapeutic value of Mycoplanecin. Accordingly, we considered it desirable to seek derivatives of Mycoplanecin which would retain all, or a substantial proportion, of the Mycoplanecin activity but which have improved absorption on administration to animals.
We have now surprisingly discovered that modification or replacement of the N-(.alpha.-ketobutyryl)-N-methylvalyl group of formula: ##STR3## gives compounds having improved biological availability and value as intermediates in the preparation of other Mycoplanecin derivatives.